1. Technical Field
This invention relates to the field of internal combustion engine diagnostics and control. More particularly, it relates to a low cost circuit for internal combustion engine diagnostics using an ionization signal.
2. Discussion
Combustion of an air/fuel mixture in the combustion chamber of in an internal combustion (IC) engine produces ions that can be detected. If a voltage is applied across a gap of a spark plug, these ions are attracted and will create a current. This current produces a signal called an ionization current signal IION that may be detected. After the ionization current signal IION is detected, the signal may be processed and sent to a powertrain control module (PCM) for engine diagnostics and closed-loop engine combustion control. A variety of methods have been used to detect and process the ionization current signal IION that are produced in a combustion chamber of an internal combustion engine.